Two independent teams of researchers found that putting the silvery metal scandium under extreme pressure makes it into a superconductor at a temperature higher than any other element on its own
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| Scandium is the high-temperature record holder for a pure element superconducting Phil Degginger / Alamy Stock Photo |
The silvery metal scandium can be made into a superconductor without having to be mixed with other substances, and this occurs at higher temperatures than for any other element. The process still requires extreme cold and pressure, but the discovery could help us engineer more practical materials with zero electrical resistance.
Superconductors – materials that conduct electricity without the electrical resistance that leads to wasted energy – have been studied intensively for over a century because of their promise to enable perfectly efficient electronics. For early superconductors, the challenge was that they only worked when cooled to extremely low temperatures, so all devices powered by them had to be kept in powerful fridges.
More recently, researchers discovered that the superconducting properties of some materials can be turned on at higher temperatures, called critical temperatures, by changing the materials’ chemical composition or putting them under pressure. There is still no definitive consensus on how to engineer a material that superconducts at room temperature, but all claims about it so far, many of which have been controversial, involve extreme pressure.
Now, two research teams have independently found that when it comes to putting pressure on materials made of only one element, scandium superconducts at the highest temperature yet.
“Solids made of a single element are some of the simplest and cleanest systems for studying superconductivity, but so far they all seemed to have critical temperatures below -243°C,” says Jianjun Ying at the University of Science and Technology of China who worked on one of the experiments. The other research team was led by Changqing Jin at the Chinese Academy of Sciences.
In both experiments, researchers compressed a small piece of scandium between two diamonds to exert extreme pressure. Compressing scandium changes the arrangement of its atoms, and at extreme pressures it gets deformed in just the right way for some electrons inside of it to participate in superconductivity more readily at higher temperatures. In one experiment, the highest pressure was approximately 75 per cent of the pressure at the centre of the earth.
Both teams repeated the squeezing procedure many times, at slightly different temperatures and pressures, measuring the scandium’s electrical resistance each time. When the material’s resistivity dropped to zero, meaning electricity could flow through it without energy loss, they knew it had become superconducting.
Now, two research teams have independently found that when it comes to putting pressure on materials made of only one element, scandium superconducts at the highest temperature yet.
“Solids made of a single element are some of the simplest and cleanest systems for studying superconductivity, but so far they all seemed to have critical temperatures below -243°C,” says Jianjun Ying at the University of Science and Technology of China who worked on one of the experiments. The other research team was led by Changqing Jin at the Chinese Academy of Sciences.
In both experiments, researchers compressed a small piece of scandium between two diamonds to exert extreme pressure. Compressing scandium changes the arrangement of its atoms, and at extreme pressures it gets deformed in just the right way for some electrons inside of it to participate in superconductivity more readily at higher temperatures. In one experiment, the highest pressure was approximately 75 per cent of the pressure at the centre of the earth.
Both teams repeated the squeezing procedure many times, at slightly different temperatures and pressures, measuring the scandium’s electrical resistance each time. When the material’s resistivity dropped to zero, meaning electricity could flow through it without energy loss, they knew it had become superconducting.
For Ying’s team this happened at a pressure of 260 gigapascals and -237°C, while Jin and his colleagues found the highest critical temperature to be -242°C, at 283 gigapascals of pressure. Accounting for small differences in the equipment the team used, the two measurements are essentially equivalent, says Jin.
“When I was first starting out as a physicist, [achieving superconductivity at] these temperatures would have been unthinkable for a pure element,” says M. Brian Maple at the University of California, San Diego.
Maple says that the high pressure requirements may make immediate applications for superconducting scandium impractical. But, he adds that understanding how deforming the material’s structure changes its critical temperature could help researchers engineer new superconductors in the future.
References:
arXiv DOI: 10.48550/arXiv.2302.14378, DOI: 10.48550/arXiv.2303.01062
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